//afl_ext 2017-2019
precision lowp float;
varying vec2 vUv;
uniform float iTime;
uniform vec2 iResolution;
uniform vec2 iMouse;
uniform sampler2D iChannel0;
uniform sampler2D iChannel1;
uniform sampler2D tDiffuse;

#define iterations 17
#define formuparam 0.53

#define volsteps 20
#define stepsize 0.1

#define zoom   abs(cos(cos(iTime/10.)))
#define tile   0.850
#define speed  0.001

#define brightness 0.0015
#define darkmatter 0.300
#define distfading 0.730
#define saturation 0.850


void main()
{
    //get coords and direction
    vec2 uv=vUv.xy/iResolution.xy-.5;
    uv.y*=iResolution.y/iResolution.x;
    vec3 dir=vec3(uv*zoom,1.);
    float time=iTime*speed+.25;

    //mouse rotation
    float a1=.5+iMouse.x/iResolution.x*2.;
    float a2=.8+iMouse.y/iResolution.y*2.;
    mat2 rot1=mat2(cos(a1),sin(a1),-sin(a1),cos(a1));
    mat2 rot2=mat2(cos(a2),sin(a2),-sin(a2),cos(a2));
    dir.xz*=rot1;
    dir.xy*=rot2;
    vec3 from=vec3(1.,.5,0.5);
    from+=vec3(time*2.,time,-2.);
    from.xz*=rot1;
    from.xy*=rot2;

    //volumetric rendering
    float s=0.1,fade=1.;
    vec3 v=vec3(0.);
    for (int r=0; r<volsteps; r++) {
        vec3 p=from+s*dir*.5;
        p = abs(vec3(tile)-mod(p,vec3(tile*2.))); // tiling fold
        float pa,a=pa=0.;
    for (int i=0; i<iterations; i++) {
    p=abs(p)/dot(p,p)-formuparam; // the magic formula
    a+=abs(length(p)-pa); // absolute sum of average change
    pa=length(p);
    }
    float dm=max(0.,darkmatter-a*a*.001); //dark matter
    a*=a*a; // add contrast
    if (r>6) fade*=1.-dm; // dark matter, don't render near
    //v+=vec3(dm,dm*.5,0.);
    v+=fade;
    v+=vec3(s,s*s,s*s*s*s)*a*brightness*fade; // coloring based on distance
    fade*=distfading; // distance fading
    s+=stepsize;
    }
    v=mix(vec3(length(v)),v,saturation); //color adjust
    vec4 texel = texture2D( tDiffuse, vUv );
    gl_FragColor = vec4(texel.rgb * v*.01,v);

}






